STOP CHARGING MY CREDIT CARD

I received a free 30 day trail of vitamins with wen products in Feb 2012. They lure customers with free offers and they store our credit card info. In March, they sent a refill. I called to Wen and returned its product and they didn't charge my card, but I have hard time stopping scheduled credit card charges for the GRC vitamins. They sent me package and I returned it without opening. Now they tell it will take 4-6 weeks.This is scam what small businesses like GRC vitamins do in US having no regulation from government.